A carburetor or a fuel injector is a device that causes the creation of a mixture of fuel and air in a predictable and efficient ratio. In the case of a carburetor fuel is introduced into an air volume which is subsequently transported to the combustion space within a cylinder. In the case of a fuel injector the fuel is sometimes injected directly into the cylinder combustion space, but in other situations is injected into an air volume that is then sent to the cylinder as is typical with carburetion systems. In either case, the fuel/air ratio is dependent on throttle setting.
Controlling airflow volume and velocity within a carburetor largely determines the parameters relating to throttle response, engine power, fuel atomization, specific fuel consumption and the operating consistency of the engine. When an engine is operated at a constant throttle setting under a constant load and in constant atmospheric conditions, the carburetor can be of a simple design while still permitting the engine to operate efficiently. In the real world of motor vehicle operation the load changes frequently as the vehicle accelerates, decelerates and changes elevation. Maintaining the appropriate airflow volume and velocity under these changing conditions is extremely challenging.
The basic problem of carburetor air flow and fuel mixture dynamics may be better understood with reference to FIGS. 10 and 11. A prior art carburetor 41 is depicted in FIG. 10 with the throttle slide 46 shown in an approximately half open position. As the throttle slide is moved in the direction of arrow 54 the throttle is moved towards a further closed position, thereby further restricting the amount of air passing through the carburetor. Atmospheric air enters the inlet 51 of the carburetor, travelling generally in the direction of arrow 52. Initially the paths followed by the air, such as paths 53, 59 and 60 are substantially parallel, but as the carburetor inlet wall 61 narrows in cross sectional width, and the air encounters the lower edge 62 of the throttle slide 46, the path followed by any molecule of air becomes substantially different from other air molecules. As the air passes over float bowl 43, fuel particles, such as fuel particle 57, initially travelling in the direction of arrow 55 are entrained in the flowing air to form the fuel/air mixture needed for engine combustion.
The fuel/air mixture is actually composed of many closely adjacent air molecules and fuel particles, all travelling through the carburetor along diverse paths. For example, path 59 represents a region of air molecules that travel along a relatively straight path 58 at a relatively constant velocity. The adjacent path 60 follows a completely different path 63 in which the velocity changes dramatically along the path 63. The amount of fuel entrained along either path 59 or 60 cannot be calculated with precision. Complicating matters is the creation of voids such as region 56, in which the velocity of the air/fuel mixture may be relatively low while the fuel/air density in region 56 may be relatively high. The result is a nonlinear throttle response as the slide 46 is moved, along with an unpredictable interaction with any reversionary wave generated during the combustion process.
The prior art carburetor 41 is depicted in FIG. 11 with the throttle slide 46 shown in an approximately fully open position. The air entering along path 59, instead of following the relatively constant path 58 shown in FIG. 10 instead follows a much more circuitous path 64. The air entering along path 60 follows a relatively less circuitous path than in the case depicted in FIG. 10. The entrained fuel particle 67 may be substantially identical to the fuel particle 57 shown in FIG. 10, but may also be substantially different in size and velocity at a similar point with respect to the carburetor float bowl 43. A void region 66 is present in a different location than the previously cited void region 56. In other words, the movement of the throttle slide 46 creates a substantially different dynamic of fuel/air mixture flow due to turbulence within the carburetor 41, a condition which is only made less predictable by the introduction of relatively more turbulent flow within the carburetor by any means.
Another device used to create an air/fuel mixture for use in an internal combustion engine is the throttle body 93 as illustrated in FIGS. 14, 15 and 16. The throttle body controls air flow to an intake manifold by operating a butterfly valve 94 within a generally cylindrical housing 95. Air enters through a front or upstream opening 97 and exits the housing 95 via downstream opening 96. A throttle position sensor 98 controls the position of the butterfly valve 94 in response to a signal from or mechanical interaction an accelerator or other throttle control accessible to the operator of a vehicle.
A prior art throttle body 93 is depicted in FIG. 17 with the butterfly valve 94 shown in an approximately half open position. As the butterfly valve is moved in the direction of arrow 99 the throttle is moved towards a further closed position, thereby further restricting the amount of air passing through the throttle body. Atmospheric air enters the inlet 97 of the throttle body, travelling generally in the direction of arrow 100. Initially the paths followed by the air, such as paths 101, 102 and 103 are substantially parallel, but as the carburetor inlet wall 104 narrows in cross sectional width, and the air encounters the leading edge 105 of the butterfly valve 94, the path followed by the air becomes substantially different for each molecule.
For example, path 101 represents a region of air molecules that travel along a relatively straight path 106 at a relatively constant velocity. The adjacent path 102 follows a longer path 107. Path 103 follows a substantially more circuitous path in which the velocity changes dramatically along the path 108. The presence of the valve 94 creates voids such as region 109, resulting in a nonlinear throttle response as the valve 94 is moved, along with the unpredictable influence exerted on any reversionary wave generated during the combustion process.
The prior art throttle body 93 is depicted in FIG. 18 with the butterfly valve 94 shown in an approximately fully open position. The air entering along path 110, instead of following the relatively constant velocity path 106 shown in FIG. 17 instead follows a much more circuitous path 111. The air entering along path 112 follows a relatively less circuitous path than in the case depicted in FIG. 17 for entry path 103. A void region 113 is present in a substantially similar location to the previously cited void region 109. The rotation of the valve 94 creates a different level of turbulence within the air flow due to turbulence within the throttle body 93, a condition which is not predictable and which is not conducive to creating an orderly exit of air from the throttle body outlet 96.
Numerous devices have been developed for placement within the fuel/air transport stream to address the problems caused by variations in throttle setting and the load placed on the engine. A common theme in such devices is a belief that the creation of relatively greater turbulence within the air/fuel will promote better combustion and fuel economy. For example, U.S. Pat. No. 3,952,776, entitled “Fluid Flow Device”, inserts a variable cross section member into the throat of a carburetor in an effort to increase air flow velocity on the intake side of the carburetor.
U.S. Pat. No. 4,359,035, entitled “Intake Manifold Fuel Atomizing Screen”, uses a mechanical strainer 11 in an effort to create a homogenous fuel/air mixture on the intake side of the carburetor. The strainer is three dimensional and can incorporate various geometries. This device is supposed to redirect the flow in numerous directions, including upstream.
U.S. Pat. No. 4,491,106, entitled “Throttle Configuration Achieving High Velocity Channel at Partial Opening”, presents numerous butterfly valve geometries to increase intake airflow.
U.S. Pat. No. 4,620,951, entitled “Slideable Throttle Valve Assembly for a Carburetor and Associated Method of Operation”, discloses a slide valve that attempts to improve performance by improving the seal between the slide valve and the groove within which the slide valve operates. This arrangement theoretically forces the intake air to flow under the valve and theoretically prevents intake air from flowing around the sides of the valve.
U.S. Pat. No. 5,636,612, entitled “Adjustable Air Velocity Stacks for Two Stroke Fuel Injected Engines” discloses a slideable throttle plate defined by front and rear surfaces 38 and 40 which permit a series of ports 52-62 to be opened or closed to a desired degree.
U.S. Pat. No. 5,718,198, entitled “Slide Throttle Valve for an Engine Intake System” discloses a sliding throttle plate 26 which includes a series of openings 28 that are followed by a series of tubular channels 18 that lead to the intake plenum 23. The channelized or at least separated flow follows a plate that serves as a throttle adjustment.
U.S. Pat. No. 5,879,595, entitled “Carburetor Internal Vent and Fuel Regulation Assembly” discloses a vent within a carburetor that constantly monitors air pressure within the carburetor and adjusts airflow in response thereto. The '595 carburetor does not use a throttle valve. U.S. Pat. No. 7,111,607, entitled, “Air Intake Device of Internal Combustion Engine” discloses an engine intake device in which a cylinder head has two intake ports that are divided by a partition that divides the intake ports into upper and lower passages. U.S. Pat. No. 7,665,442 “Throttle Plate for use with Internal Combustion Engine” discloses vortex generators 14 that surround an airflow passageway to create turbulence.
While the '198 and '612 patents show a throttle plate followed by channels, neither is used within a carburetor and both require the use of a perforated throttle plate. The '035 patent creates the most turbulent flow possible while introducing some pressure loss in the system, and fails to control or direct the turbulent flow in any predictable manner. These characteristics also true of the '442 patent, although a well defined vortex possesses more predictable airflow effects than a screen or baffle.
U.S. Pat. No. 7,690,349, entitled “Throttle Body Spacer for use with Internal Combustion Engines” discloses four fins placed in the fuel/air flow path immediately following the throttle. The fins are bent or twisted in an effort to create a circular or spiral flow in the region following the spacer. This mechanism is intended to promote relatively more thorough fuel atomization. U.S. Pat. No. 8,220,444, entitled “System for Improving the Efficiency of an Internal Combustion Engine of a Vehicle”, discloses a set of curved longitudinal fins within the intake and exhaust manifold intended to accelerate airflow to and from the engine.
The prior art discloses many attempts to realign the airflow through a carburetor throat. Efforts to increase turbulence are frequently presented in a mistaken effort to promote mixing of air and fuel in a process analogous to stirring. Unfortunately, efforts to create turbulence tend to create an unpredictable array of voids and eddies which do not promote either mixing or a predictable throttle response. What is not disclosed in the prior art is a method of consistently forming and controlling channelized, laminar airflow at a relatively low Reynold's Number in the region immediately following the throttle plate and regardless of throttle position.